1. Field of the Invention
The present invention relates to a column unit for performing temperature control of a separation column, and a gas chromatography device provided with the column unit.
2. Description of the Related Art
Many of the gas chromatography devices that are currently on the market accommodate a separation column in a forced convection oven that reduces the temperature distribution inside the oven by causing the air inside to convect by force, and to perform temperature control of the separation column. Heating of the separation column by such a forced convection oven has advantages that thermal uniformity inside the oven may be easily achieved, and also, that the influence of the ambient temperature is not easily received.
On the other hand, since the oven itself has a high heat capacity, there is a disadvantage that it is difficult to increase the rate of temperature increase and the rate of temperature decrease of the column. The rate of temperature increase affects the time required until the temperature inside the oven becomes stable, and if the rate of temperature increase is low, the time required until an analysis is started becomes long, thereby increasing the time required for the analysis. Also, in the case of performing a temperature increase analysis of performing an analysis while raising the temperature of the separation column at a constant rate, if the rate of temperature increase is low, the time required for one temperature increase analysis becomes long. Therefore, to reduce the time required until the start of an analysis or the time required for an analysis, the rate of temperature increase of the separation column has to be increased. However, the rate of temperature increase of a gas chromatography device that uses a forced convection oven, which is currently in practical use, is 60° C./min or less.
In recent years, gas chromatography devices provided with a heat-transfer temperature control unit for performing temperature control of a separation column by heat transfer from a heater without involving air are being proposed and applied (see U.S. Pat. Nos. 6,682,699, 6,530,260, and 5,298,225). The heat capacity of such a heat-transfer temperature control unit is smaller than that of a convection oven, and a temperature increase analysis may therefore be performed at an increased rate, but since the heat capacity thereof is small, the influence of the ambient temperature is easily perceptible. Accordingly, a heat insulation treatment is performed on the temperature control unit including a separation column by covering the unit with an insulating material or by enclosing the unit with a housing so that influence of the ambient temperature is not easily received.
According to the gas chromatography device, the separation column may have to be cooled to or below the temperature of the room, it is in depending on an analysis sample. In the case of cooling the separation column to or below the room temperature in the forced convection oven, the oven itself has to be cooled to or below the room temperature by introducing cooled carbon dioxide or nitrogen gas, and the cooling mechanism will be large and complicated, and also, as with heating, it is difficult to performing cooling at a high rate.
With the gas chromatography device provided with a heat-transfer temperature control unit, if a heat insulation treatment is performed around the separation column to reduce the influence of the ambient temperature on the separation column, the rate of temperature increase may be increased, but the efficiency of heat dissipation to surroundings is reduced, and the rate of cooling is reduced. In the case of repeatedly performing the temperature increase analysis, when a temperature increase analysis is performed, the separation column has to be cooled to a predetermined temperature to perform the next temperature increase analysis, and the total time necessary for one temperature increase analysis is the sum of the temperature increase analysis time and the cooling time. Accordingly, to increase the operating rate at the time of repeatedly performing the temperature increase analysis, it is important that the cooling time is reduced together with the temperature increase time.
Cooling of a separation column by providing a heat-transfer temperature control unit with a Peltier device is proposed (see “Gas chromatography using resistive heating technology”, A. Wang et. al, Journal of Chromatography, Vol. 1261, pp. 46-57, 2012). By providing a Peltier device to the temperature control unit, the cooling efficiency for the separation column may be increased while enhancing the heat insulation of the separation column. However, since generally, a Peltier device cannot be used at a high temperature of 200° C. or higher, it is difficult to use the temperature control unit provided with a Peltier device for the purpose of analyzing for example a high-boiling component.